$OpenBSD: patch-xor_c,v 1.1 2017/05/04 21:40:48 espie Exp $
return value found in more recent sources

Index: xor.c
--- xor.c.orig
+++ xor.c
@@ -635,7 +635,7 @@ int xor_evolve(struct level* plevel)
     pmover = plevel->stack_first;
 
     if(pmover == NULL)
-	return;
+	return 0;
 
     px = pmover->x;
     py = pmover->y;
